The present invention relates to a method and apparatus for producing high quality laser-induced damage images in transparent objects.
A number of techniques for creating a variety of patterns on the surface and inside of transparent substrates using pulsed laser radiation are well known.
One publication disclosing such techniques is the Russian invention # 321422 to Agadjanov et. al., published on Nov. 16, 1970 (#140454529-33). The invention concerns a method of manufacturing decorative products inside a transparent material by changing the material structure by laser radiation. As disclosed, by moving a material relative to a focused laser beam, it is possible to create a drawing inside the material.
U.S. Pat. No. 4,092,518 to Merard discloses a method for decorating transparent plastic articles. This technique is carried out by directing a pulsed laser beam into the body of an article by successively focusing the laser beam in different regions within the body of the article. The pulse energy and duration is selected based upon the desired extent of the resulting decorative pattern. The effect of the laser is a number of three dimensional xe2x80x9cmacro-destructionxe2x80x9d (fissures in the material of the article) appearing as fanned-out cracks. The pattern of the cracks produced in the article is controlled by changing the depth of the laser beam focus along the length of the article. Preferably, the article is in the form of a cylinder, and the cracks are shaped predominantly as saucer-like formations of different size arranged randomly around the focal point of the optical system guiding a laser beam. The device used to carry out this technique is preferably a multi-mode solid-state, free-running pulse laser used in conjunction with a convergent lens having a focal length from 100 to 200 mm.
U.S. Pat. No. 4,843,207 to Urbanek et al., discloses a method of creating controlled decorations on the surface of a hollow symmetrical transparent article. This technique is preferably carried out on glass. The glass is preconditioned with a coating on the outer surface of the glass being approximately 1.2 mm thick and made of a material having at least 75% absorption of laser radiation. The technique is also carried out using a laser having a wave of length of 0.5 to 2 microns acting upon the external coating through the wall of the cylindrical glass article. The laser beam moves so that it is focused on the surface of the cylinder, and moves about the axis of symmetry of the cylinder to irradiate the aforementioned surface coating. As a result, the irradiated portions of the surface coating go through a phase change and a pattern is formed.
U.S. Pat. No. 5,206,496 to Clement et al. discloses a method and apparatus for providing in a transparent material, such as glass or plastic, a mark which is visible to the naked eye or which may be xe2x80x9cseenxe2x80x9d by optical instruments operating at an appropriate wavelength. The Clement et al. patent describes a method and apparatus for producing a subsurface marking which is produced in a body such as bottle, by directing into the body a high energy density beam and bringing the beam to focus at a location spaced from the surface, so as to cause localized ionization of the material. In the preferred embodiment the apparatus includes a laser as the high energy density beam source. The laser may be a Nd-YAG laser that emits a pulsed beam of laser radiation with a wavelength of 1064 nm. The pulsed beam is incident upon a first mirror that directs the beam through a beam expander and a beam combiner to a second mirror. A second source of laser radiation in the form of a low power Hexe2x80x94Ne laser emits a secondary beam of visible laser radiation with a wavelength of 638 m. The secondary beam impinges upon the beam combiner where it is reflected toward the second reflecting surface coincident with the pulsed beam of laser radiation from the Nd-YAG laser. The combined coincident beams are reflected at the reflecting surface via reflecting two other surfaces to a pair of movable mirrors for controlling movement of the beam. The beam then passes through a lens assembly into the body to be marked.
Soviet patent publication 1838163 to P. V. Agrynsky, et. al discloses a process for forming an image in a solid media by processing of the optically transparent solid material by a beam of radiation with changeable energy for creation of the image.
WIPO Patent Document No. 96/30219 to Lebedev et al. discloses a technology for creating two- or three-dimensional images inside a polymer material using penetrating electromagnetic radiation. The technology can be used for marking and for producing decorative articles and souvenirs. Specifically, laser radiation is used as the penetrating radiation, and carbonizing polymers are used as the polymer material. By these means, it is possible to produce both black and half-tone images in the articles.
U.S. Pat. No. 5,575,936 to Goldfarb discloses a process and apparatus where a focused laser beam causes local destruction within a solid article, without effecting the surface thereof. The apparatus for etching an image within a solid article includes a laser focused to a focal point within the article. The position of the article with respect to the focal point is varied Control means, coupled to the laser, and positioning means are provided for firing the laser so that a local disruption occurs within the article to form the image within the article.
U.S. Pat. No. 5,637,244 to Erokhin discloses a technique which depends on a particular optical system including a diffraction limited Q-switched laser (preferably a solid-state single-mode TEM00) aimed into a defocusing lens having a variable focal length to control the light impinging on a subsequent focusing lens that refocuses the laser beam onto the transparent article being etched. The laser power level, operation of the defocusing lens, and the movement of the transparent article being etched are all controlled by a computer. The computer operates to reproduce a pre-programmed three-dimensional image inside the transparent article being etched. In the computer memory, the image is presented as arrays of picture elements on various parallel planes. The optical system is controlled to reproduce the stored arrays of picture elements inside the transparent material. A method for forming a predetermined half-tone image is disclosed. Accordance to the method, microdestructions of a first size are created to form a first portion of the image and microdestruction of a second size different from the first size are created to form a second portion of the image. Different sizes of microdestructions are created by changing the laser beam focusing sharpness and the radiation power thereof before each shot.
U.S. Pat. No. 5,886,318 to A. Vasiliev and B. Goldfarb discloses a method for laser-assisted image formation in transparent specimens, which consists in establishing a laser beam having different angular divergence values in two mutually square planes. An angle between the plane with a maximum laser beam angular divergence and the surface of the image portion being formed is changed to suit the required contrast of an image.
EPO Patent Document 0743128 to Balickas et al. disclose a method of marking products made of transparent materials which involves concentration of a laser beam in the material which does not absorb the beam, at a predetermined location, destruction of the material by laser pulses and formation of the marking symbol by displacement of the laser beam. Destruction of the material at that location takes place in two stages. In the first stage, the resistance of the material to laser radiation is altered, while, in the second stage, destruction of the material takes place at that location.
Russian patent publication RU 20082288 to S. V. Oshemkov discloses a process for laser forming of images in solid media by the way of focusing of laser radiation in a point inside a sample which differs by following: with the aim to save the surface and the volume of the sample before the definite point and creation of three dimensional images, the sample is illuminated with the power density higher than the threshold of volume breakdown and moving the sample relatively to the laser beam in three orthogonal directions.
U.S. Pat. No. 6,087,617 to Troitski et al. discloses a computer graphic system for producing an image inside optically transparent material. An image reproducible inside optically transparent material by the system is defined by potential etch points, in which the breakdowns required to create the image in the selected optically transparent material are possible. The potential etch points are generated based on the characteristics of the selected optically transparent material. If the number of the potential etch points exceeds a predetermined number, the system carries out an optimization routine that allows the number of the generated etch points to be reduced based on their size. To prevent the distortion of the reproduced image due to the refraction of the optically transparent material, the coordinates of the generated etch points are adjusted to correct their positions along a selected laser beam direction.
U.S. patent application Ser. No. 09/354,236 to Troitski discloses a laser-computer graphic system for generating portrait and 3-D reproductions inside optically transparent material. Accordance to the invention, production of a portrait of the same resolution like a computer image is made by using a multi-layer picture. Points of every layer are arranged so that the distance between adjacent etch points are equal to the minimal distance between etch points that can be provided without the breakage of the material. Every layer is parallel with respect to the portrait plane, and distance between parallel planes is set equal to minimal distance at which the breakage of the material does not occur.
U.S. patent application Ser. No. 09/356,252 to Troitski discloses method and laser system for generating the etch points with improved characteristics inside optically transparent material. According to the invention two laser beams are directed at the same focal point inside transparent material. The first and the second laser beams have energy levels below an energy level sufficient to cause breakdown of the material but combination of their energy levels is greater than breakdown threshold. The first and the second laser beams are directed at the same point in directions generally perpendicular to one another.
U.S. patent application Ser. No. 09/557,306 to Troitski discloses method and laser system for creation of laser-induced damages to produce high quality images. Accordance to the invention, a laser-induced damage is produced by simultaneously generating breakdowns in several separate focused small points inside the transparent material area corresponding to this etch point. Damage brightness is controlled by variation of a number of separate focused small points inside the transparent material area.
U.S. patent application Ser. No. 09/583,454 to Troitski discloses method and laser system controlling breakdown process development and space structure of laser radiation for production of high quality laser-induced damage images. Accordance to the invention, at the beginning an applied laser radiation level just exceeds an energy threshold for creating a plasma condition in the material, and thereafter the energy level of the applied laser radiation is just maintain the plasma condition. Accordance to another method a laser generates a TEMmn radiation. The values of the integers m and n are controlled and determined so as to reproduce particular gray shades for a particular point of an image.
U.S. Pat. No. 5,392,309 to Nishimae et al. describes a laser apparatus, which can provide a completely circular laser beam by providing a laser beam, which is symmetrical with respect to an unstable direction. A laser apparatus includes an unstable resonator having a total. reflection mirror and a take-out mirror, and further includes shading means for shading a disturbed phase portion of a laser beam so as to derive exclusively a light having a uniform phase by shading the disturbed phase portion of the beam emitted from the resonator or the beam in the resonator.
U.S. Pat. No. 5,473,475 to Sweatt et al. discloses a method for changing the cross section of a laser beam. The invention is directed to a laser beam reshaping system comprising a mirror having a laser beam reflective surface for converting an incident laser beam having a circular cross-section to a beam having a polygonal cross-section.
U.S. Pat. No. 5,477,554 to Yoshii et al. describes a phase shift device and laser apparatus utilizing the same. The device divides a passing area of a laser beam into plural area and provides the laser beam passing through the plural areas with predetermined phase difference thereby providing a laser beam of a smaller beam spot diameter while maintaining a large depth of focus without change in the numerical aperture of the imaging optical system, and which is adapted to be placed in an appropriate position in the optical path thereby satisfactory correcting the astigmatism of the laser light source, and a laser apparatus employing the phase shift device.
U.S. Pat. No. 5,506,858 to Takenaka et al. describes a laser system with transverse mode selecting output coupler. The laser system includes a stable resonator and a laser medium provided within the resonator, the stable resonator comprising a coupling mirror and a total reflector disposed in an opposed relation to the coupling mirror, the coupling mirror having a partially reflecting portion located centrally and an anti-reflecting portion located around the partially reflecting portion.
U.S. Pat. No. 5,644,589 to Anthon describes two solid state laser structures which are optimized for multimode operation. The first laser structure has a plurality of normal incidence optically transmissive surfaces in the laser cavity. The most reflective one of those normal incidence surfaces is disposed at the optical center of the laser cavity. The gain medium is centered in the sub-cavity defined by a cavity mirror and the optical center. In the second laser structure, there are no normal incidence surfaces in the laser cavity, and the gain medium is disposed at the optical center of the laser cavity.
U.S. Pat. No. 5,745,511 to Leger describes a phase grating and mode-selecting mirror for a laser. The invention teaches how to design and fabricate a custom phase-conjugation mirror, which will accommodate a fundamental-mode beam profile of arbitrary profile in Cartesian x and y transverse dimensions. The invention also teaches how to design and fabricate a diffractive mirror for use as a custom phase-conjugation mirror, which is a mirror that will reflect a wave front having arbitrary (i.e., a complex mode profile that is not necessary only real but may have imaginary components) field at the mirror surface. The invention also teaches using an additional phase element in a laser resonator system having a custom phase-conjugation mirror in order to enhance the phase differential between the fundamental mode and higher-order mode wave fronts over and above the result possible with a single CPCM alone.
U.S. Pat. No. 5,982,806 to Yamaguchi et al. discloses a laser beam converter for converting a laser beam with a single high-order transverse mode into a laser beam with a desired intensity distribution and laser resonator for producing a laser beam with a single high-order transverse mode. The laser resonator is provided with a regulating plate of a high-order transverse mode, which is constructed so as to produce a laser beam in a single high-order transverse mode.
Majority of patents mentioned above disclose the production methods of large etch points with strong or smoothed sharp star structure. For production of laser-induced damage images by using corresponding etch points it is necessary to use specific methods. Particularly, U.S. patent application Ser. No. 09/354,236 to Troitski discloses the method for production of a portrait with the same resolution like a computer image by creation of a multi-layer picture. These multilayer portraits are looked like perfect images if they have enough large sizes. But when portrait sizes decline the quality of multi-layers portraits goes down.
For production of a single-layer high quality portrait it is necessary to produce enough small etch points without sharp star structure. In this case it is possible to reproduce portrait of high resolution and to transmit right gray shades using only single-layer. Particularly, enough small etch points without sharp star structure can be produced using methods disclosed in U.S. patent application Ser. No. 09/356,252 (now abandoned) to Troitski, U.S. patent application Ser. No. 09/557,306 to Troitski (now U.S. Pat. No. 6,333,486), and in U.S. patent application Ser. No. 09/583,454 to Troitski. However using the fact that desirable portrait should have only one layer it is possible to create new more low-price but more effective methods and systems for production of small etch points without sharp star structure, which can be used to create single-layer portraits.
The present patent application discloses the method and the system for production of single-layer high quality portraits with reduced sharp star structure inside transparent materials.
The present invention has its principal task to disclose a method, systems and apparatus for creating single-layer high quality laser-induced damage portraits inside a transparent material.
One or more embodiments of the invention comprise a method and an apparatus for producing etch points with a size reduced along beam direction by using special optics focusing laser radiation without defacement due to refraction of a focused laser beam at a surface of a transparent article.
One or more embodiments of the invention comprise a laser system for producing single-layer portraits by using the cumulative effect without raise of time production creating smaller etch points of smoother sharp star structure.
One or more embodiments of the invention comprise a method for producing single-layer portraits based on generation of small smoothed etch points of determined sizes and on control of their brightness without variation of their final required sizes.
One or more embodiments of the invention comprise a laser etching system producing high quality single-layer laser-induced damage portraits inside transparent material using generation of small smoothed etch points of determined sizes and dynamic control of their brightness without variation of their final required sizes.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings, which follows, when considered with the attached figures.